Photographic film and method of treating same



Patented Mar. 21, 1939 i rno'rocnarmo FILM AND METHOD or I rename SAME Donald 1:. Allison, Beverly mus, CaliL, assignor to Detracolor Ltd., a corporation of Nevada 1 No Drawing. Application February 15, 1935 erial No. 6,641

2 Claims. (01. 95-6) This application is a continuation in part of my copending application Serial #629,874 filed August 22, 1932, now Patent No. 2,034,220 Mar. 17, 1936, wherein the substancehereof is dis- 5 closed but not claimed.

My invention relates broadly to the art of color photography and more particularly to a film or other medium for use in that art which will render a photograph in color upon very simple treatment after exposure. Specifically I employ what may be termed a latent dye, or a leuco base as more generally known to the dye art, in-combination with 'a photographic emulsion or other light sensitive substance suitable for photographic use. i

It is an object of myinvention to provide a photographic film which can be exposed in the usual way and'which will have an invisible or latent dye therein of such a nature that upon subsequent treatment it will assume a predeter- 0 mined color to give a photograph in that color.

It is a further object of my invention to control the potential color of the photograph by a proper selection of the latent dye or leuco base used in the making ofthe-photographic 5 medium so that it will be possible to secure a photograph in any color desired by using a substantially standard or uniform process of treat- 1 ing the exposed film. I

It is also an object of my inventionto provide 'A 30 a method'of treating an exposed film of the type described so as to bring out the color of the latent dye or leuco base. I It is another object of my invention to pro.-

vide a film having impregnated therein a leuco 35 base, which said film has not lost any of'its photographic sensitivity by reason of the presence of the leuco base.

'My invention finds application in bothbranches of the photographic art, namely, still photography and motion picture photography, and will be found to be equally applicable to both of these branches. It has long been recognized that the coldness of the black and white images obtained by the customary'methods of photography employing the usual type of film or plate is not desirable and various remedies for this objection have beenflpropose'd-and tried. Themost common means used for coloring photographs, whether they be from a still camera or from a motion picture camera, are toning, dyeing and dye-toning, all of which are cumbersome and otherwise rather unsatisfactory from boththe artistic and the commercial viewpoint. The advantage of having the coloring medium in the film before exposure is'obvious when it is realized that this can be accomplished during the manufacture of the film.

The chief obstacle in color work heretofore, particularly in amateur work, is that the meth- 1o ods of coloring have been so complicated and unstable that it required a highly specialized staff and equipment to operate a given process and even then, uniform results were difiicult of attainment. It is therefore an object of my invention to provide a film which can be exposedin the manner now customarily used, and which can then have its latent color brought out by a process so simple and uniform in its operation that anyone familiar with, and equipped to do ordinary developing can treat the film in the course of development so as to bring out a colored image.

'Thesejand some of the other objects and advantages of my invention will become apparent from the following detailed description of a preferred form of my invention.

In making a film "according to my invention I find it preferable to mix into the gelatine solution containing a light sensitive salt, such as silver bromide for instance, a solution of a suitable leuco base.' The leuco base is chosen according to the color desired and with due regard to availability and cost. If desired the coated film may be soaked in a solution of leuco base to impregnate it sufilciently for satisfactory use, or if preferred the dry leuco base can be mixed in the coating solution. The particular state of the leuco'base at the time of using and the exact time of impregnating form no part of my invention, and can be varied at will depending on localized conditions in the production of the finished film ready for exposure. Broadly speaking all leuco bases of the aniline dyes may be used in the practice of my invention, but I have found that certain of this class of dyes are more satisfactory than others, in that they are more stable. As is well known to the chemical'and dye arts aniline dyesmay be subdivided into numerous series or families, each of which is again subdivisible into the many dyes' commonly known.

Of these various series or families I have found that the triphenylmethane series is extremely well adapted for use in my inventions; that is to say; when the respective leuco bases of many of these dyes are impregnated in the photographic emulsion, they will upon suitable treatment as hereinafter set forth, give stable colors in the photographic images As is well known in the chemical art, the fundamental or basic structural formula for the leuco of the triphenylmethane dyes can be represented thust QrO all of the various sub-seriesor derivatives being where T, T' and T" are substituted or unsub- 'stituted amino groups and R and R are alkyl,

alkoxy, hydrogen or hydroxyl groups.

The alkyldiamino'triphenylmethane derivatives have the general formula of where T and T are substituted oii unsubstituted amino groups, R- and R are hydrogen, alkyi, alkoxy or hydroxyl groups.

The halogenated triphenylmethane derivatives have the general formula of.

QrO

Where T and T' are substituted-or unsubstituted amino groups, R and R are'hydrogen, alkyl, alkoxy or hydroxyl groups and X, Y, Z are halogens or hydrogen, of which one must be a halogen and all may be halogens. Familiar examples of these three derivatives are fuchsin, malachite green and glacier blue respectively.

After the light sensitive emulsion has been impregnated with a suitable leuco base, say, forexample, glacier blue of the halogenated derivatives or some other suitable leuco base from the triphenylrnethane series the'fllm is exposed in the usual manner. It will be evident that in the operation of my invention the leuco base can be used. in either a negative or positive film or both if desired in which latter case the negative 5 is treated to bring out its color before it is printed to the positive raw stock. In .that the negativeis usually used primarily for producingblack and white' positive prints which are subsequently colored, I will describe my invention as applied to a process which contemplates the production of the usual black and white negative using a standard film'with no leuco base therein. This negative after developing, fixing, washing and drying is then used to print to a positive film which I have impregnated with a leuco base as hereinbefore described. When in this description I use the term expose it is to be deemed to include exposure of the negative in a camera and also the exposure of the positive stock. to the 20 printing light coming to it through the, negative,

depending on the context of the sentence.

The positive stock after printing contains a latent silver image and throughout the emulsion a suitable leuco base. It is then developed in any standard developer such as "elon (monomethyl p-aminophenol sulphate) or hydroquinone or other suitable substances and given a thorough. acid water wash to arrest further development and to wash out surplus developing solution. At this point the film may be then treated with a suitable "fixing solution, although this may not be necessary, depending on the subsequent processing. The film at this stage' contains a black silver image which shades down .to gray in its lesser densities with clear spaces where no light passed through the negative in printing. The

leuco base is still unafiected at this point of the process. The film is now immersed in a solution which will oxidize the free silver to a silver salt which will in turn mordant the leuco base in situ. This oxidation step causes the leuco base to assume its predetermined color. A solu- "tlon suitable for oxidizing the leuco base to its color. dye form and oxidizing the free silver to a substance which is a mordant for the dye in situ as the color is formed may be made up as follows:

Potassiumierricyanide gram 5 Chromic acid gram 1 Copper sulphate gram 2 Hydrochloric acid (cone) c.c 5 Water to ma n- 1 I have also found that a. solution of chlorine water or bromine water will serve admirably as an oxidizing agent to convert the silver to a salt which will mordant the dye in site. I

The film is now given a thorough water wash to remove excess oxidizer and all dye not mordanted in the images, and is immersed in a fixing solution containing sodium thiosulphate and tannic acid which removes the translucent silver salt by formand fixing agents may be used without in any way departing from theproper scope of my invention.

For instance my invention is readily applicable 1 believe, are all within the scopeot my invention as to the so-called bi-pack method 0! color photo:- raphy wherein two color selection negatives are secured, say, one recording blue color values and the other one recording red color values. These two negatives are by means well known in the ,art printed in register to opposite sides of a positive having alight sensitive emulsion on each side thereof. One emulsion may have a latent blue dye or leuco base impregnated therein, and the other may have a latent red dye or leuco base impregnated therein. The film is. then treated as hereinbeiore mentioned for a single emulsion with the result that on one side oi! the positive a red image is produced and on the opposite side a complimentary image in blue is produced; the result being that when projected a two-color'picture is thrown on the screen.

These and other variations of my invention which will be evident to those skilled in the art I- defined by the appended claims.

; I claim as my invention; I

.1. In a. photographic film the combination of: an emulsion carrying a light sensitive silver salt and the leuco base of a triaminotriphenylmeth ane derivative. of the general structure a where 'r, 'r' and 'r" are'substituted or unsubstituted amino groups, and R. and R are hydrogen, alkyl, alkoxy or hydroxyl groups.

. 2. The method of producing a photograph in color which includes: exposing to light a film having a light sensitive silver salt emulsion layer thereon containing the leuco base of a rosaniline, 

